Geo 101N 1st Edition Lecture 15Outline of Last Lecture I. Igneous Rocks (iclicker question included)II. Igneous TexturesIII. Extrusive v IntrusiveIV. Classifying Igneous RocksV. Cooling Time of MagmaVI. Fractional Chemical ReactionVII. Bowens Reaction SeriesVIII. Volcano EruptionsIX. Volcano TypesOutline of Current Lecture X. Basaltic LavaXI. Andesitic &Rhyolitic LavaXII. Pyroclastic EruptionsXIII. Pyroclastic Debris from Andesitic/Rhyolitic Eruptions XIV. Other DepositsXV. Volcanic GasXVI. Composite VolcanosXVII. Volcanic HazardsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Current LectureX. Basaltic Lavaa. Also known as Mafic b. High in Fe and Mg but low in silicac. Low explosive properties, low volatile contentd. Lava tube: when part of the flows interiorsolidifies & eventually molten lava flows onlythrough a tubee. Pahoehoe: surface texture of basalticlava flow; cause by warm flows, pastysurface wrinkles into a smooth surfacef. A’a’: jumbled broken lavaXI. Andesitic &Rhyolitic lava flowsa. Higher silica content, higher viscocityb. Lava cannot flow easilyc. Andesitic lava forms big domes above thevent that are lumpy and very slowly flowdown the volcanod. Blocky flowXII. Pyroclastic Eruptionsa. Explosive-felsicpyroclastic debrisb. Pyroclastic debris-lava that flies in to the air and freezes basaltic magma containing dissolved volatiles (ie water)-bubbles of these gases burst & eject clots; form dramatic fountains-landslides, mudflows common1. Lapilli: pea-sized fragments of glassy lava (cinders)2. Blocks: apple to refrigerator sized fragmentsc. Bombs: blocks formed when soft lava squirts out of the vent & then solidifies; often have a streaked or polished surface-house sizedXIII. Pyroclastic Debris from Andesitic/Rhyolitic Eruptions a. The more viscous may be more gas rich; these tend to be very explosiveb. Ash: particles smaller than 2mm made from glass shards, formed when frothing lava explosively breaks up during eruptionsc. Pumice lapilli: angular pumice formed from frothy lavad. Accretionary: snowball like lumps of ash formed when ash mixes with water in the air& stick togethere. Pyroclastic flow: lava rushing down the flank of the volcano in an avalanche like flowf. Tephra: unconsolidated deposits of pyroclastic grains, regardless of sizeg. Tuff: ash or ash + lapilli buried & transformed into coherent rockh. Ignimbrite: sheet of tuff formed from a pyroclastic flowXIV. Other Depositsa. Volcanic debris flow: moves downslope like wet concreteb. Lahar: very wet, ash-rich debris flows becomes a slurryXV. Volcanic Gasa. H2O, CO2, SO2 & H2S (hydrogen sulfide)b. Up to 9% of a magma may consist of gaseousXVI. Composite volcanosa. Associated with subduction zonesb. Explosive nature of eruptions is the result of the water in the lavaXVII. Volcanic Hazards-lava flows-volcanic gases-ash cloud-pyroclastic